The first collection day will last about 1-2 hours. For the second collection day, subjects will be randomized into group A or B to determine the order of sockets tested during data collection on the second day. Subjects in group A will use their original prosthesis in the first collection while group B subjects will use their duplicate socket prosthesis. Subjects will switch to the other socket for the second collection session. The second day is expected to last about 3-4 hours. Each session will consist of the following: